Stable Isotope Dilution Gas Chromatography–Mass Spectrometry for Quantification of Thymoquinone in Black Cumin Seed Oil

Johnson-Ajinwo, Okiemute Rosa; Li, Wen-Wu

Abstract

Black cumin seed (Nigella sativa L.) is a widely used spice and herb, where thymoquinone (2-isopropyl-5-methyl-1,4-benzoquinone) is the major bioactive compound. Here, a stable isotope dilution (SID) gas chromatography–mass spectrometry (GC–MS) technique was developed for the quantification of thymoquinone. A doubly deuterated thymoquinone ([2H2]-thymoquinone) was synthesized for the first time with more than 93% deuteration degree shown by mass spectrometry and proton nuclear magnetic resonance (1H NMR). This compound was used as an internal standard for the quantification of thymoquinone using a SID GC–MS method. The validation experiment showed a recovery rate of 99.1 ± 1.1% relative standard deviation (RSD). Standard addition and external calibration methods have also been used to quantify thymoquinone, which cross-validated the developed stable isotope dilution assay (SIDA). In comparison to external calibration and standard addition methods, the SIDA method is robust and accurate. The concentration of thymoquinone in five marketed black cumin seed oils ranged between 3.34 and 10.8 mg/mL by use of SID GC–MS.

Citation

Johnson-Ajinwo, O. R., & Li, W. (2014). Stable Isotope Dilution Gas Chromatography–Mass Spectrometry for Quantification of Thymoquinone in Black Cumin Seed Oil. Journal of Agricultural and Food Chemistry, 62(24), 5466-5471. https://doi.org/10.1021/jf500357x

• Journal Article Type: Article
• Online Publication Date: Jun 5, 2014
• Publication Date: Jun 18, 2014
• Deposit Date: Jun 13, 2023
• Journal: Journal of Agricultural and Food Chemistry
• Print ISSN: 0021-8561
• Electronic ISSN: 1520-5118
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 62
• Issue: 24
• Pages: 5466-5471
• DOI: https://doi.org/10.1021/jf500357x
• Keywords: General Agricultural and Biological Sciences; General Chemistry; Nigella sativa; thymoquinone; stable isotope dilution; GC−MS; quantification